Stress-induced Premature Senescence Model Research Articles

Temporal inhibition of the electron transport chain attenuates stress-induced cellular senescence by prolonged disturbance of proteostasis in human fibroblasts.

We previously developed a stress-induced premature senescence (SIPS) model in which normal human fibroblast MRC-5 cells were treated with either the proteasome inhibitor MG132 or the vacuolar-type ATPase inhibitor bafilomycin A1 (BAFA1). To clarify the involvement of mitochondrial function in our SIPS model, MRC-5 cells were treated with MG132 or BAFA1 along with an inhibitor targeting either the electron transport chain complex I or complex III, or with a mitochondrial uncoupler. SIPS induced by MG132 or BAFA1 was significantly attenuated by short-term co-treatment with the complex III inhibitor, antimycin A (AA), but not the complex I inhibitor, rotenone or the mitochondrial uncoupler, carbonyl cyanide 3-chlorophenylhydrazone. By co-treatment with AA, mitochondrial and intracellular reactive oxygen species levels, accumulation of protein aggregates and mitochondrial unfolded protein responses (UPRmt ) were remarkably suppressed. Furthermore, AA co-treatment suppressed the hyperpolarization of the mitochondrial membrane and the induction of mitophagy observed in MG132-treated cells and enhanced mitochondrial biogenesis. These findings provide evidence that the temporal inhibition of mitochondrial respiration exerts protective effects against the progression of premature senescence caused by impaired proteostasis.

Senolytics rejuvenate the reparative activity of human cardiomyocytes and endothelial cells

Abstract Background Senescent cells have emerged as bona fide drivers of ageing and age-related cardiovascular disease, with senescent cells accumulating in the aged heart and following damage/injury. We have shown that removal of senescent cells using senolytics can rejuvenate the regenerative capacity of the aged heart. Purpose We investigate the effects of cell senescence and action of the senolytics, Dasatinib (D) and Quercetin (Q), on human cardiomyocyte and endothelial cell viability, survival, proliferation, angiogenesis and senescence in vitro. Methods We developed a transwell insert co-culture stress-induced premature senescence model system in vitro. Doxorubicin was used to induce premature senescence to cardiac stromal progenitor cells or HUVECs, which were seeded on the bottom chamber. In separate well plates, untreated cells (non-senescent) were seeded on the bottom chamber and acted as control. Human iPSC-cardiomyocytes (iPSC-CMs) or HUVECs were seeded on the top chamber insert. Co-cultures were left for 7 days and then iPSC-CMs or HUVECs in the top chamber were analysed for viability, proliferation and markers of senescence, and the conditioned medium analysed for SASP factors. The cultures were then treated with D+Q (0.5μM D with 20μM Q) for 3 days to clear the senescent cells in the bottom chamber. Then 7 days later the iPSC-CMs or HUVECs in the top chamber were analysed for viability, proliferation and the markers of senescence, and conditioned medium analysed for SASP factors (total of 17 days). Results Co-culture of iPSC-CMs with senescent cells led to decreased iPSC-CM viability (64±11% vs. 100±3% control; p<0.05) and proliferation (5±2% vs. 11±1% control; p<0.05). There was no increased senescence in co-cultured iPSC-CMs. Treatment with senolytics D+Q resulted in rescue of viability (79±23% 17d co-culture+D+Q; 64±9% 17d co-culture; 100±4% 17d control) and proliferation (7±2% 17d co-culture+D+Q; 3±0.3% 17d co-culture; 8±0.3% 17d control). Similar effects were observed with HUVECs, which showed decreased viability (83±5% vs. 100±6% control; p<0.05) and proliferation (21±7% vs. 44±7% control; p<0.05) when co-cultured with senescent HUVECs. Treatment with senolytics ameliorated HUVEC viability (61±22% 17d co-culture+D+Q; 21±12% 17d co-culture; 100±5% 17d control), proliferation (30±5% 17d co-culture+D+Q; 22±4% 17d co-culture; 48±4% 17d control) and angiogenesis (Score relative to control: 1.1±0.5 D+Q conditioned media; 0.2±0.1 senescent cell conditioned media; 1.0±0.3 control media). Luminex analysis of the senescent cell conditioned media revealed upregulation of SASP factors, but the level of SASP factors were reduced with application of D+Q. Conclusion We show that D+Q senolytics have therapeutic potential in rejuvenating the reparative activity of cardiomyocytes and endothelial cells. These results open the path to further studies on using senolytic therapy in age-related cardiac deterioration and rejuvenation. Funding Acknowledgement Type of funding sources: Other. Main funding source(s): Heart Research UK

Fermentation broth of Serpula similis protect cells from oxidative stress-induced senescence via AMPK-dependent autophagy restoration

Serpula similis is an interesting member of Hymenomycetes in association with bamboo clumps. However, the functions of Serpula similis on cellular senescence are not clear yet. In this study, the protective effect of fermentation broth of Serpula similis (FeBrSS) on cellular senescence-induced by oxidative stress and the potential mechanism was studied. The stress-induced premature senescence model was established by hydrogen peroxide, and model cells were subjected to the intervention with FeBrSS. As a result, we found that FeBrSS administration certainly repressed activity of senescence associated β-Galactosidase and expression of senescence-associated genes. Interestingly, the effects of FeBrSS are related to the restoration of impaired autophagy via activation of AMP-activated protein kinase (AMPK) other than via mTORC1 pathway. Together, our study demonstrated for the first time that FeBrSS have the effects of inhibiting senescence via autophagy restoration which occurs due to activation of AMPK pathway, and therefore, supported that autophagy plays a critical role in anti-aging. Our findings expanded the list of fermentation broth of fungus of significance and may provide new evidence or strategies for developing new drugs for anti-aging.

Optimization of oxidative stress-induced premature senescence model using VH10 fibroblasts for assessment of natural compounds

The diverse physiological functions of histamine are mediated through distinct histamine receptors. In this study we investigated the role of H2R and H4R in the effects of histamine on the production of reactive oxygen species by phagocytes in whole blood.Changes in reactive oxygen species (ROS) production by whole blood phagocytes after treatment with histamine, H4R agonists (4-methylhistamine, VUF8430), H2R agonist (dimaprit) and their combinations with H4R antagonist (JNJ10191584) and H2R antagonist (ranitidine) were determined using the chemiluminescence (CL) assay. To exclude the direct scavenging effects of the studied compounds on the CL response, the antioxidant properties of all compounds were measured using several methods (TRAP, ORAC, and luminol–HRP–H2O2 based CL).Histamine, 4-methylhistamine, VUF8430 and dimaprit inhibited the spontaneous and OZP-activated whole blood CL in a dose-dependent manner. On the other hand, only VUF8430 was able to inhibit PMA-activated whole blood CL. Ranitidine, but not JNJ10191584, completely reduced the effects of histamine, 4-methylhistamine and dimaprit. The direct scavenging ability of tested compounds was negligible.Our results demonstrate that the inhibitory effects of histamine on ROS production in whole blood phagocytes were caused by H2R. Our results also suggest that H4R agonists in concentrations higher than 10− 6 M may also influence ROS production via binding to H2R.

P16 I NK 4a Deletion Ameliorates Damage of Intestinal Epithelial Barrier and Microbial Dysbiosis in a Stress-Induced Premature Senescence Model of Bmi-1 Deficiency.

This study aimed to determine whether Bmi-1 deficiency leads to intestinal epithelial barrier destruction and microbiota dysfunction, which members of the microbial community alter barrier function with age, and whether p16INK4a deletion could reverse the damage of intestinal epithelial barrier and microbial dysbiosis. Intestines from Bmi-1–deficient (Bmi-1–/–), Bmi-1 and p16INK4a double-knockout (Bmi-1–/–p16INK4a–/–), and wild-type mice were observed for aging and inflammation. Duolink Proximity Ligation Assay, immunoprecipitation, and construction of p16INK4a overexpressed adenovirus and the overexpressed plasmids of full-length, mutant, or truncated fragments for occludin were used for analyzing the interaction between p16INK4a and occludin. High-throughput sequencing of V4 region amplicon of 16S ribosomal RNA was conducted using intestinal microbiota. We found Bmi-1 deficiency destructed barrier structure, barrier function, and tight junction (TJ) in intestinal epithelium; decreased the TJ proteins; increased tumor necrosis factor α (TNF-α)–dependent barrier permeability; and up-regulated proinflammatory level of macrophages induced by intestinal microbial dysbiosis. The transplantation of fecal microbiota from wild-type mice ameliorated TJ in intestinal epithelium of Bmi-1–/– and Bmi-1–/–p16INK4a–/– mice. Harmful bacteria including Desulfovibrio, Helicobacter, and Oscillibacter were at a higher level in Bmi-1–/– mice. More harmful bacteria Desulfovibrio entered the epithelium and promoted macrophages-secreted TNF-α and caused TNF-α–dependent barrier permeability and aging. Accumulated p16INK4a combined with occludin at the 1st–160th residue in cytoplasm of intestinal epithelium cells from Bmi-1–/– mice, which blocked formation of TJ and the repair of intestinal epithelium barrier. P16INK4a deletion could maintain barrier function and microbiota balance in Bmi-1–/– mice through strengthening formation of TJ and decreasing macrophages-secreted TNF-α induced by Desulfovibrio entering the intestinal epithelium. Thus, Bmi-1 maintained intestinal TJ, epithelial barrier function, and microbiota balance through preventing senescence characterized by p16INK4a accumulation. The clearance of p16INK4a-positive cells in aging intestinal epithelium would be a new method for maintaining barrier function and microbiota balance. The residues 1–160 of occludin could be a novel therapeutic target for identifying small molecular antagonistic peptides to prevent the combination of p16INK4a with occludin for protecting TJ.

Mitochondrial gene COX2 methylation and downregulation is a biomarker of aging in heart mesenchymal stem cells.

The mitochondria have been proven to be involved in processes of aging; however, the mechansims through which mitoepigenetics affect the cytological behaviors of cardiomyocytes during the aging process are not yet fully understood. In the present study, two senescence models were constructed, replicative senescence (RS) and stress-induced premature senescence (SIPS), using human heart mesenchymal stem cells (HMSCs). First, the differences in age-related gene expression levels and telomere length were compared between the HMSCs in the RS and SIPS models by PCR. Subsequently, protein expression and the mitochondrial DNA (mtDNA) methylation status of cytochrome c oxidase subunit II (COX2) was measured by western blot analysis and bisulfite genomic sequencing (BSP). Finally, the value of the DNA methyltransferase (Dnmt) inhibitor, 5-aza-2′-deoxycytidine (AdC), in delaying the senescence of HMSCs was evaluated. It was found that the p16, p27 and p53 mRNA expression levels increased in the senescent cells, whereas p21 mRNA expression did not. It was also found that telomere shortening only occurred in the RS model, but not in the SIPS model. Along with the senescence of HMSCs, COX2 gene methylation increased and its protein expression level significantly decreased. It was demonstrated that AdC inhibited COX2 methylation and downregulated COX2 expression. The addition of exogenous COX2 or the administration of AdC promoted cell proliferation and delayed cell aging. On the whole, the present study demonstrates that COX2 methylation and downregulation are biomarkers of HMSC senescence. Thus, COX2 may have potential for use as a therapeutic target of cardiovascular diseases and this warrants further investigation.

Stress-induced premature senescence activated by theSENEX gene mediates apoptosis resistance of diffuse large B-cell lymphoma via promoting immunosuppressive cells and cytokines.

BackgroundThe underlying cause of relapsed and refractory (r/r) diffuse large B‐cell lymphoma (DLBCL) is usually related to apoptosis resistance to antitumor drugs. The recent years have provided lots of evidence that tumor cells may undergo stress‐induced premature senescence (SIPS) in response to chemotherapy, but how SIPS affects lymphoma cells remains inconclusive.MethodsFifty‐two DLBCL patients, including 6 newly diagnosed (ND), 17 complete remissions (CR), and 29 (r/r), were enrolled in this study. We used a senescence‐associated‐β‐galactosidase (SA‐β‐Gal) staining kit for senescence staining. Suppressive immune cells including regulatory T cells (Treg) and myeloid‐derived suppressor cells (MDSC) were detected by flow cytometry (FCM). Secreted cytokines were measured by ELISA Kit and SENEX gene expression was detected by a quantitative real‐time polymerase chain reaction. We used 40 nM doxorubicin to induce the SIPS model of DLBCL in vitro. Apoptosis and proliferation activity of senescent LY8 cells were respectively detected by FCM and CCK8. SENEX gene was silenced by RNA interference.ResultsThe proportion of senescent lymphoma cells was significantly increased in r/r DLBCL patients, concomitant with increased Treg, MDSC, and various secreted cytokines with proinflammatory and immunosuppressive effects. The SENEX gene was significantly elevated in the SIPS model. Senescent DLBCL cells had good antiapoptotic ability and proliferative activity accompanied by increased immunosuppressive cytokines. Interestingly, when we silenced the SENEX gene in the DLBCL cell line, the results were the opposite to the above.ConclusionSIPS activated by the SENEX gene mediates apoptosis resistance of r/r DLBCL via promoting immunosuppressive cells and cytokines.

TGF-β1/IL-11/MEK/ERK signaling mediates senescence-associated pulmonary fibrosis in a stress-induced premature senescence model of Bmi-1 deficiency

To study whether TGF-β1/IL-11/MEK/ERK (TIME) signaling mediates senescence-associated pulmonary fibrosis (SAPF) in Bmi-1-deficient (Bmi-1−/−) mice and determines the major downstream mediator of Bmi-1 and crosstalk between p16INK4a and reactive oxygen species that regulates SAPF, phenotypes were compared among 7-week-old p16INK4a and Bmi-1 double-knockout, N-acetylcysteine (NAC)-treated Bmi-1−/−, Bmi-1−/−, and wild-type mice. Pulmonary fibroblasts and alveolar type II epithelial (AT2) cells were used for experiments. Human pulmonary tissues were tested for type Ι collagen, α-smooth muscle actin (α-SMA), p16INK4a, p53, p21, and TIME signaling by using enzyme-linked immunosorbent assay (ELISA). Our results demonstrated that Bmi-1 deficiency resulted in a shortened lifespan, ventilatory resistance, poor ventilatory compliance, and SAPF, including cell senescence, DNA damage, a senescence-associated secretory phenotype and collagen overdeposition that was mediated by the upregulation of TIME signaling. The signaling stimulated cell senescence, senescence-related secretion of TGF-β1 and IL-11 and production of collagen 1 by pulmonary fibroblasts and the epithelial-to-mesenchymal transition of AT2 cells. These processes were inhibited by anti-IL-11 or the MEK inhibitor PD98059. NAC treatment prolonged the lifespan and ameliorated pulmonary dysfunction and SAPF by downregulating TIME signaling more than p16INK4a deletion by inhibiting oxidative stress and DNA damage and promoting ubiquitin-proteasome degradation of p16INK4a and p53. Cytoplasmic p16INK4a accumulation upregulated MEK/ERK signaling by inhibiting the translocation of pERK1/2 (Thr202/Tyr204) from the cytoplasm to the nucleus in senescent fibroblasts. The accumulation of collagen 1 and α-SMA in human lungs accompanied by cell senescence may be mediated by TIME signaling. Thus, this signaling in aging fibroblasts or AT2 cells could be a therapeutic target for preventing SAPF.

P16INK4a Deletion Ameliorated Renal Tubulointerstitial Injury in a Stress-induced Premature Senescence Model of Bmi-1 Deficiency

To determine whether p16INK4a deletion ameliorated renal tubulointerstitial injury by inhibiting a senescence-associated secretory phenotype (SASP) in Bmi-1-deficient (Bmi-1−/−) mice, renal phenotypes were compared among 5-week-old Bmi-1 and p16INK4a double-knockout, and Bmi-1−/− and wild-type mice. Fifth-passage renal interstitial fibroblasts (RIFs) from the three groups were analyzed for senescence and proliferation. The effect of Bmi-1 deficiency on epithelial-to-mesenchymal transition (EMT) was examined in Bmi-1-knockdown human renal proximal tubular epithelial (HK2) cells, which were treated with concentrated conditioned medium (CM) from the fifth-passage renal interstitial fibroblasts (RIFs) of above three group mice or with exogenous TGF-β1. Our results demonstrated that p16INK4a deletion largely rescued renal aging phenotypes caused by Bmi-1 deficiency, including impaired renal structure and function, decreased proliferation, increased apoptosis, senescence and SASP, DNA damage, NF-κB and TGF-β1/Smad signal activation, inflammatory cell infiltration, and tubulointerstitial fibrosis and tubular atrophy. P16INK4a deletion also promoted proliferation, reduced senescence and SASP of RIFs and subsequently inhibited EMT of Bmi-1-knockdown HK2 cells. TGF-β1 further induced the EMT of Bmi-1-knockdown HK2 cells. Thus, p16INK4a positive senescent cells would be a therapeutic target for preventing renal tubulointerstitial injury.

Modulation of PPARγ provides new insights in a stress induced premature senescence model.

Peroxisome proliferator-activated receptor gamma (PPARγ) may be involved in a key mechanism of the skin aging process, influencing several aspects related to the age-related degeneration of skin cells, including antioxidant unbalance. Therefore, we investigated whether the up-modulation of this nuclear receptor exerts a protective effect in a stress-induced premature senescence (SIPS) model based on a single exposure of human dermal fibroblasts to 8-methoxypsoralen plus + ultraviolet-A-irradiation (PUVA). Among possible PPARγ modulators, we selected 2,4,6-octatrienoic acid (Octa), a member of the parrodiene family, previously reported to promote melanogenesis and antioxidant defense in normal human melanocytes through a mechanism involving PPARγ activation. Exposure to PUVA induced an early and significant decrease in PPARγ expression and activity. PPARγ up-modulation counteracted the antioxidant imbalance induced by PUVA and reduced the expression of stress response genes with a synergistic increase of different components of the cell antioxidant network, such as catalase and reduced glutathione. PUVA-treated fibroblasts grown in the presence of Octa are partially but significantly rescued from the features of the cellular senescence-like phenotype, such as cytoplasmic enlargement, the expression of senescence-associated-β-galactosidase, matrix-metalloproteinase-1, and cell cycle proteins. Moreover, the alterations in the cell membrane lipids, such as the decrease in the polyunsaturated fatty acid content of phospholipids and the increase in cholesterol levels, which are typical features of cell aging, were prevented. Our data suggest that PPARγ is one of the targets of PUVA-SIPS and that its pharmacological up-modulation may represent a novel therapeutic approach for the photooxidative skin damage.

Anti-photoaging potential of Botulinum Toxin Type A in UVB-induced premature senescence of human dermal fibroblasts in vitro through decreasing senescence-related proteins

This study was aimed to evaluate the anti-photoaging effects of Botulinum Toxin Type A (BoNTA) in Ultraviolet B-induced premature senescence (UVB-SIPS) of human dermal fibroblasts (HDFs) in vitro and the underlying mechanism. We established a stress-induced premature senescence model by repeated subcytotoxic exposures to Ultraviolet B (UVB) irradiation. The aging condition was determined by cytochemical staining of senescence-associated β-galactosidase (SA-β-gal). The tumor suppressor and senescence-associated protein levels of p16INK-4a, p21WAF-1, and p53 were estimated by Western blotting. The G1 phase cell growth arrest was analyzed by flow cytometry. The mRNA expressions of p16, p21, p53, COL1a1, COL3a1, MMP1, and MMP3 were determined by real-time PCR. The level of Col-1, Col-3, MMP-1, and MMP-3 were determined by ELISA. Compared with the UVB-irradiated group, we found that the irradiated fibroblasts additionally treated with BoNTA demonstrated a decrease in the expression of SA-β-gal, a decrease in the level of tumor suppressor and senescence-associated proteins, a decrease in the G1 phase cell proportion, an increase in the production of Col-1 and Col-3, and a decrease in the secretion of MMP-1 and MMP-3, in a dose-dependent manner. Taken together, these results indicate that BoNTA significantly antagonizes premature senescence induced by UVB in HDFs in vitro, therefore potential of intradermal BoNTA injection as anti-photoaging treatment still remains a question.

Comparative Effects of Biodynes, Tocotrienol-Rich Fraction, and Tocopherol in Enhancing Collagen Synthesis and Inhibiting Collagen Degradation in Stress-Induced Premature Senescence Model of Human Diploid Fibroblasts

Biodynes, tocotrienol-rich fraction (TRF), and tocopherol have shown antiaging properties. However, the combined effects of these compounds on skin aging are yet to be investigated. This study aimed to elucidate the skin aging effects of biodynes, TRF, and tocopherol on stress-induced premature senescence (SIPS) model of human diploid fibroblasts (HDFs) by determining the expression of collagen and MMPs at gene and protein levels. Primary HDFs were treated with biodynes, TRF, and tocopherol prior to hydrogen peroxide (H2O2) exposure. The expression of COL1A1, COL3A1, MMP1, MMP2, MMP3, and MMP9 genes was determined by qRT-PCR. Type I and type III procollagen proteins were measured by Western blotting while the activities of MMPs were quantified by fluorometric Sensolyte MMP Kit. Our results showed that biodynes, TRF, and tocopherol upregulated collagen genes and downregulated MMP genes (P < 0.05). Type I procollagen and type III procollagen protein levels were significantly increased in response to biodynes, TRF, and tocopherol treatment (P < 0.05) with reduction in MMP-1, MMP-2, MMP-3, and MMP-9 activities (P < 0.05). These findings indicated that biodynes, TRF, and tocopherol effectively enhanced collagen synthesis and inhibited collagen degradation and therefore may protect the skin from aging.

Ginsenoside Rg1 protects human fibroblasts against psoralen- and UVA-induced premature senescence through a telomeric mechanism

This study was aimed to investigate the protective effects of ginsenoside Rg1 on 8-methoxypsoralen(8-MOP)/Ultraviolet A (UVA)-induced premature senescence in human fibroblasts, and the underlying mechanism. We established a stress-induced premature senescence model by 8-MOP/UVA irradiation. The aging condition was determined by histochemical staining of senescence-associated β-galactosidase (SA-β-gal). Relative telomere length was calculated by the ratio of the amount of telomere DNA versus single copy DNA by real-time polymerase chain reaction, and protein levels of p-P53, p21(WAF-1) and p16(INK-4a) were estimated by Western blotting. Compared with the 8-MOP/UVA treatment group, we found that the irradiated fibroblasts pretreated with ginsenoside Rg1 demonstrated a decrease in the expression of SA-β-gal, a downregulation in the level of senescence-associated proteins, and a deceleration in telomere shortening. Taken together, these results suggest that ginsenoside Rg1 significantly antagonizes premature senescence induced by 8-MOP/UVA in fibroblasts.

Ultraviolet B exposure triggers premature senescence in human skin fibroblasts.

Objective To develop a model of ultraviolet B (UVB)-induced premature senescence in human skin fibroblasts (HSF) so as to assess the relationship between stress-induced premature senescence and tumorigenesis. Methods The irradiation dose and frequency were optimized for the induction of prema-ture senescence. HSF were irradiated with UVB of 10 mJ/cm~2 once daily for 5 days, and unirradiated HSFs served as the control. After the last irradiation, cell proliferation was determined by MTT assay on day 3, 4, 5,6 and 7, SA β-Gal staining was performed to evaluate the senescence state of cells on day 3, and RT-PCR to detect the expressions of three senescene-associated genes, including fibronectin (FN), osteonectin (ON) and smooth muscle 22 (SM22) on day 3. Results After five exposures to UVB, HSF showed biological characteris-tics of senescence. As assessed by MTT assay, there was a loss of replicative potential in irradiated cells. The proportion of SA-β-gal-positive cells was 82.0% in UVB-stressed HSFs and 33.7% in the control cells (P < 0.01). The mRNA levels of FN, ON and SM22 were upregulated by 2.7, 2.0 and 2.3 folds respectively in irra-diated HSF compared with the control cells (all P < 0.05). Conclusion A stress-induced premature senes-cence model is established using HSF by repeated exposure to subcytotoxic UVB. Key words: Ultraviolet; Fibroblasts; Cell aging

The gene expression profile of psoralen plus UVA-induced premature senescence in skin fibroblasts resembles a combined DNA-damage and stress-induced cellular senescence response phenotype

After a finite number of population doublings, normal human cells undergo replicative senescence accompanied by growth arrest. We previously described a model of stress-induced premature senescence by treatment of dermal fibroblasts with psoralen plus UVA, a common photodermatological therapy. Psoralen photoactivation has long been used as a therapy for hyperproliferative skin disorders. The repetitive therapeutical treatment is accompanied by premature aging of the skin. Treatment of fibroblasts in vitro with 8-methoxypsoralen (8-MOP) and subsequent ultraviolet A (UVA) irradiation results in growth arrest with morphological and functional changes reminiscent of replicative senescence. For gene expression profiling in two strains of human skin fibroblasts after PUVA treatment, we used a low-density DNA array representing 240 genes involved in senescence and stress response. Twenty-nine genes were differentially expressed after PUVA treatment in the two strains of human skin fibroblasts. These genes are involved in growth arrest, stress response, modification of the extracellular matrix and senescence. This study contributes further to the elucidation of the PUVA model and its validation as a useful stress-induced premature senescence model aiming to characterize the premature senescence of fibroblasts and to identify biomarkers that could be applied in vivo.